Weathering and Erosion — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Which best explains why soil on a steep hill erodes faster than soil on flat ground?
A) The hill has more rain
B) Gravity pulls water and soil downhill faster on steep slopes
C) Flat ground has no gravity
D) Hills are made of softer rock
Steeper slopes increase water velocity and gravitational pull on soil particles, causing faster erosion.
2. A statue made of marble has become rough and pitted after 200 years outdoors. What most likely caused this?
A) Physical weathering from sunlight
B) Chemical weathering from acid rain
C) Erosion from strong winds
D) Deposition of new minerals
Acid rain dissolves the calcium carbonate in marble, pitting and roughening the surface over time.
3. Which human activity can speed up erosion the most?
A) Planting trees on hillsides
B) Building terraces on slopes
C) Clearing forests for farmland
D) Adding mulch to gardens
Removing trees exposes bare soil, eliminating root systems that anchor it. This dramatically increases erosion by rain and wind.
4. What is the correct order of events that forms a delta?
A) Deposition, erosion, weathering
B) Weathering, erosion, deposition
C) Erosion, deposition, weathering
D) Deposition, weathering, erosion
Rock weathers → erosion transports sediment → deposition builds the delta where the river slows.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Terracing farmland on hillsides helps slow erosion by creating flat steps.
Terraces reduce slope angle and water velocity, dramatically slowing the downhill movement of soil.
2. A sea arch forms when waves erode both sides of a rocky headland.
Waves attacking both sides of a headland (a point of land jutting into the sea) eventually carve a sea arch through it.
3. Oxidation is a type of chemical weathering that causes iron-bearing rocks to turn red.
Iron + oxygen + water → iron oxide (rust/hematite). This gives many desert rocks and soils their characteristic red or orange color.
4. The movement of large amounts of rock and soil down a slope is called mass wasting.
Mass wasting (mass movement) includes landslides, mudslides, and rockfalls — all driven by gravity.
5. Barrier islands are formed by the deposition of sand along a coast.
Barrier islands are long, narrow sand deposits parallel to the coast, built up by wave and current deposition.